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(N0 Modl.)

M. G. KELLQGG MULTIPLE SWITGHBOARD.

Patented Oct. 26,1897.

Nrrnn STATES ATENT Finca.

MILOG. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGG SVITCI'IBOARD AND SUPPLY COMPANY, OF SAME PLACE.

NI UL-TIPLE SWITCHBOARD.

SPECIFICATION forming part of lLetters Patent No. 592,379, dated October 26, 1897. Application filed July 26, 1890. Serial No. 360,090. (No model.)

To @ZZ whom it may concern:

Be it known that I, MILO G. KELLOGG, of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Multiple Switchboards for Telephone-Exchanges, of which the following is afull, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to a metallic-circuit telephone-exchange system in which there is a cord and a plug attached to the cord for each line, to which the line is connected. Said plug is inserted into the switch of another line when it is desired to switch the two lines together for conversation. Said system is called a singlecord7 system. The plug generally rests normally (or when not in use for switching) in its own special switching device.

My invention consists in a system of test ing, and in apparatus, circuit, and connections for each line,whereby the operator may expeditiously and with few movements connect her telephone to the circuit of the line when the call is indicated, may test the line wanted and at the same time ring the sub scribers signal-bell when the line is not in use, may connect the two lines together, may connect her telephone to the circuit to determine whether they are through conversation, and may disconnect the lines and place the apparatus in readiness to receive a new call. Said system and apparatus is more simple and the work required is less than in other systems devised for a similar purpose. In said system the lines test busy whether they are switched for use at any board or the line-annunciators indicate a call. I.

In the accom panyin g'drawin gs, illustrating my invention, Figure l is a diagram illustrating two switchboards andv the main-line central-office apparatus of two lines, and Fig. 2 shows in diagram a subscribers ap' paratus for his oiiice or station.

In Fig. l, A A represent sections of two multiple switchboards at the central office of the exchange. On each board is a springjack switch for each line. Each switch fhas a contact-spring which is normally in contact with a contact-point, but is separated and insulated from the point when a switch-plug is inserted into the switch, and has a third or insulated contact piece which is insulated from the other parts except by the circuit connections. This contact-piece is adapted to have a plug applied to it for calling and testing. The `switch shown inthe drawings is of well-known construction.

For each line there is a compound answering switching device located at the board wherethe cord and plug of the line are 1ocated and where its calls are to be answered.

the lines to which their double flexible con` ducting-cords are attached and which are adapted to be placed in any spring-jack vswitch at the board where they are located.

One plug is shown in its switching device and one plug is shown out of its device ready to be inserted into theswitch of any line.

`In the answering-switches, a d are cylinders, preferably of metal, adapted to receive the commutator and plug-supporting piece b. This piece may be of rubber, and is of the shape substantially as shown, and may be of Othershapes to correspond with variations in the other parts of the switches.

l, 2, 3, 4, 5, and 6 are contact-pieces insulated from each other. 2, 4, and 5 are springs. The other pieces may be rigid. Piece b has a hole or socket in which the handleot` the switch-plug may be placed. It has also two chambers to receive the bent portions of the spring-pieces 2 and 5, and has a shoulder adapted to rest on the top of d when it is moved to its lower position. In the chamber adapted to receive the spring 5 is a shoulder IOO c, on which spring V bears 'when piece b is moved to its higher position and which causes the contacts to change, as ,will be described.

Pieces 1 and 2 are mounted parallel to each other and in close juxtaposition, so that coutact between them will be made and broken by the operation of the switch-plug, as hereinafter indicated. The pairs of contacts 3 4 and 5.6 are mounted parallel to each other and in close juxtaposition, so that the contact of each pair is made and broken, as hereinafter described, by the operation of the plug. Spring 4 is connected near itsupper end to yspring 5 by means of an insulationpiece fastened to both. It therefore moves back and forth as spring 5 moves. Springs 2 and 5 are constructed and adjusted to press toward the center of piece b and will press against and be acted upon by the plug, as will be described..

The pieces b b are adapted to occupy two positions, the upper position shown in B and the lower position shown in B.

When the switch-plug is in its socket in its piece l), the piece occupies its lower position and the handle of the plug presses -on vthev springs 2 and 5, so that spring 2 is in contact with piece l, and spring 5 is out of contact with piece 6, while spring4 (which is attached to, but insulated from, spring 5) is kept out of contact with piece 3. When the switch -plu-g is withdrawn by the operator from the socket, the springs 2 and 5 will be released from the pressure of the plug-handle and (the movable piece being still in its inner position) contact between 2 and 1 is broken and that between 3 and 4 and between 5and 6 is established. When the plug is removed and the operator manipulates piece b and places it in its outer position, the contact between l and 2 still remains broken, and the shoulder c in the chamber of the piece presses spring 5 out of Contact with piece 6, and spring 4 is carried out of contact with piece 3. When, therefore, the plug is in the socket and the piece b is in its lower position, l and 2 are in contact with each other and the other y'contacts of the device are out of contact. Then the plug is out of the socket and piece b is still in its lower position, l and 2 are out of contact and 3 4 and 5 6 are in contact, respectively, and when the plug is out of the socket and the piece b is raised to 'its outer position all three pairs are out ot' contact.

The switch-plugs D D are of a usual construction of loop-switch plugs adapted to be used with the spring-jack switches shown. The outsides of the handles have a rubber'insulation. Each plug has two contact-pieces insu-lated from eachother, one, s, at the end of the plug and the other, s', along the plug cylinder-tip. When a plug is inserted into any of the switches, the piece s presses against the spring of the switch and forces the spring away from the contact-point and forms Aconnection with the sprin-g, and the 'other piece, s', of the plug forms connection with the metal frame or socket of the switch.

t t are operators telephones, R R callingbatteries, and r r resistance-coils. Eachioperator has a telephone, calling-battery, and resistance-coil, and they are connected to each other and to her answering-switches, substantially as shown 'and as will be described.

W and X are calling-annunciators, one for each line shown, and connected into their respective circuit, as will hereinafter be described. They are preferably polarized annunciators.

G G are ground connections.

Each annunciator has a pair of contactpoints normally (or when the annunciator does not indicate a call) in contact with each other, but which are separated by the annunciator while it indicates a'call. The two contact-points of a pair are marked p and q, respectively. One of them, q, is a spring-contact which is pressed by the annunciatordrop, when the drop falls, away from its corresponding contact-point p. The contactpoint p is represented as an angle-piece which passes over the spring q and is in contact with the spring when the spring is not actuated by the annunciator-drop.

The connections are substantially as follows: One side or branch of each line passes normally successively through the pairs of contact-points ot` the line-switches, passing in each case to the spring first. It then passes through the line-annunciator and the pair of contact-points of the annunciator and is then connected by one of the insulated conductors of the switch-cord to contact-piece s of the plug. 5 and l of the answering-switch of the line, the connection being made at a point between the answering-switch contact-points on the one hand and the annunciator lcontact-points on t-he other hand. The other branch of the line is connected to said third or insulated contact-pieces of its switches. It is also connected through the other conductor of the cord to contact-piece S/ of the plug andl is connected to contact-piecev 3 of the answeringswitch. Contact-piece 2 of this switch is connected to the ground. One side of the operators telephone is connected to contact-piece 4 of the answering-switch and also to the ground through her calling -battery. The other side of the ltelephone is connected through the resistance-coil r to piece 6 of the switch.

In the subscribers-station apparatus shown in Fig. 2, l is the telephone-switch. 2 is the calling-generator. 3 is the signal-receiving bell, and 4 is the subscribers telephone. The bell is an ordinary vibrating or automatic circuit breaking bell which makes and breaks its own circuit and rings while a battery of suitable strength is closed through its circuit. The contact-points and It is also connected to contact-pieces con tinually` IOO IIO

connections are substantially as shown, but

which shall perform practically the operation required. They should be such that the signal-receiving bell or its contact-points are switched or shunted out of the circuit of the line while the subscribers telephone is off the switch for use, while they are in the linecircuit while the telephone is on the switch, (or not switched for use.)

The operation of the system is as follows: lVhen the plug of a line is in its normal position in the socket of its answering-switch and the line is not switched at any board and the line-annunciator does not indicate a call, that branch of the line which passes through the several pairs of contact-points is grounded at the central oiiice. Vhen the plugis with drawn from its normal position or a plug is placed in one of its switches or the annunciator indicates a call, this ground connection is removed. Vhen the plug of a line is withdrawn from its normal position in the answering-switch, the two sides or branches of the line are brought into a closed circuit, with the operators telephone in the circuit. The connection is automatically made by the clos ing of the two pairs of contact-points 3 aand 5 G. The points 3 and 5 are connected to the two sides of the line and 4: and 6 are connected to the two sides of the telephone. The operator then by conversation nds out what line is wanted. She then places the tip S of the plug of the calling-line on the third or insulated contact-piece of the line wanted, and if the line is not switched at any board or its annunciator does not indicate a call and its normal ground connection is not broken and the subscribers telephone is not switched for use a complete circuit is established which contains the calling-battery and telephone and the subscribers circuit-break ing bell, and the bell will ring, calling the subscriber. This complete circuit is from the ground, through the battery R and telephone t and contact-points 5 G, to contact s of the plug, thence through the circuit of the line by way of the subscribers station, the normally closed contacts of the line-switches, the contacts 19 q of the annunciator, and the contacts l 2 of the plug switching device, tothe ground. The operator also will distinguish in her telephone the make and break of a bell and will know that the line is free to be connected to. She will then push the plug into the switch and by so doing disconnect the line from its normal ground connection. The test-circuit (from the operators ground, through her apparatus to the circuit of the line, and through the line to its normal ground connection) will be broken and the bell will stop ringing. The two lines are thereby connected into a metallic circuit which is cross-connected or bridged by a circuit which contains the operators telephone and resistance-coil and the subscriber wanted has been called. The operator then raises the movable piece ZJ of the answering-SW1' tch and by so doing breaks the connections at 3 4 and 5 G and removes the bridge connection. Should she wish at any time to listen into the circuit to determine whether the subscribers are through conversation, she will again establish the bridge connection by pressing in the piece b, and a part of any ltelephone-current passing over the circuit will be deiiected through her telcphone. The use of the resistance-coil is to prevent an undue amount of the current from passing through the telephone.

It will be observed that the subscribers bell will ring just so long as the operator holds the tip of the plug on the switch and when the plug is pushed into the switch the bell stops ringing.

It will also be seen that had the line been switched at any board by the use of its plug or through one of its switches, or had the subscribers telephone been switched for use and the bell thereby switched from the circuit, or had the line-annunciator indicated a call, the bell would not have rung and the operator would not have got the signal whichindicates that the line is clear. She would not, therefore, have switched the line with the line which desired the connection. A subscribers line therefore tests busy and is reserved to himself whether it is switched at any board or his telephone is switched for use or its annunciator indicates a call, and the service is more satisfactory than it would be were the test busy made by only one of these operations.

Had the subscriber taken down his telephone for use when the test was made, but the line had not been switched at the central office and the annunciator did not not indi cate,the operator would h-ear a single click in her telephone, but not a succession of' sounds. She would then know that the subscribers telephone was switched for use, but that the line was yet connected with the ground.

The operations to answer a call and complete a connection arethese: first, to remove the plug fromits normal position; second, to put the plug on the switch-cont-act of the line wanted and then push it into the switch, and,

third, to raise or move up the piece l) of thel answering-switch. In order to listen to the circuit of two lines connected together, the operator merely pushes down on the piece b of the answering-switch and her telephone is connected in a bridge to their circuit.

The calling-annunciators should be connected into their respective circuits and the operators calling-batteries should be connected in the circuits in such a direction that the calling and testing current directed to any line will not operate the annunciator and give a false signal to its operator that the subscriber has sent in a call. With electric batteries for signaling and testing and with IOO IIO

IZO

ordinary polarized annunciators for receiving calls such connection is simple and easily understood by those skilled in the art.

The calling-generator shown in Fig. 2 has an automatic device with'contact-points and connections by which the line-circuit is automatically grounded while the generator is operated with the generator in the circuit between such ground connection and the normal ground connection of the line at the central office.

by Letters Patentl. In a telephone-exchange system, a metallic-circuit telephone-line one side or branch of which is normally connected with the ground at the central office but disconnected from such ground while switched for conversation and has an annunciator normally in its circuit with contact-points by which the circuit is open while the annunciator indicates a call and the other side or branch of which is normally open at the central office,in combination with a vibrating bell at the subscribers station normally in the circuit of the line but switched or shunted from said circuit while the subscribers telephonev is switched for use and a test Wire Orcircuit at the central office containing a test receiving instrument and battery, grounded at one end and connected at its other end to a plug or device adapted to be brought into connection with the normally open end of the line, substantially as set forth.

2. In a telephone-exchange system, a metallic-circuit telephone-line one side or branch of which is normally connected to the ground at the central office but disconnected from such ground while switched for conversation and has an annunciator normally in its circuit with contact-points by which the circuit is open while the annunciator indicates a call andthe other side or branch of which is normally open at the central office, in combination with a vibrating bell at the subscriber-s station normally in the circuit of such line but switched or shunted from such circuit while the subscribers' telephone is switched for use, a test receiving instrument at the central office grounded on'one side and connected on its other side to a test plug or device adapted to be brought for testing into connection with the normally open end of the line and a battery inthe test-circuit established on testing, substantially as set forth.

3. Inatelephone-exchange system, a metalliccircuit line, one side or branch of which is normally connected with the ground at the central office and has an annunciator normally in its circuit with contact-points by which the circuit is open while the annunciator indicates a call, and the other side or branch of which is normally open at the central office, in combination with switching apparatus by which the line is disconnected from such ground connection while it is switched for conversation, a vibrating bell at the subscribers station, normally in the circuit ofthe line, a switch with contacts and connections by which the bell is shunted while the subscribers telephone is switched for use and a test wire or circuit at the central office, containing a test receiving instrument and battery, grounded at one end and connected at its other end to a plug or device adapted to be brought into connection with such normally open end of the line substantially as set forth. I claim as myinvention and desire to secure 4. In a telephone-exchange system, a metallic-circuit line one side or branch of which is normally connected with the ground at the central ofiice and has an annunciator normally in its circuit with contact-points by which the circuit is open while the annunciator indicates a call and the other side or branch of which is j normally open at the central office7 in combination with'switching apparatus by which the Q line is disconnected from such ground connec- 5 tion while switched for conversation., a vibrat- '3 ing bell at the subscribers station, normally in the circuit of the line, a switch with contacts and connections by which the bell is shunted while the subscribers telephone is switched for use, atest receiving instrument at the central office grounded on one side and connected on its other side to a test plug or device adapted to be brought into connection with g the normally open end of the lines and a battery in the circuit established on testing,'sub

: stantially asset forth.

5. In a telephone-exchange system, a lnetallic-circuit line, one side or branch of which contains a polarized annunciator having contact-points by which the circuit is open while the annunciator indicates a call and is normally grounded at the central oce but disconnected froin the ground while switched for l conversation and the other side or branch of which is normally open at the central office,

iu combination with a vibrating bell at the subscribers station normally in the circuit of the line but switched or shunted while the subscribers telephone is switched for use and a test wire or circuit at the central office containing a test receiving instrument and battery, grounded at one end and connected at the other end to a plug or device adapted to be brought into connection with the normally open end of the line, the annunciator and battery being so connected into the circuit that the battery does not operate the annunciator, substantially as set forth.

I 6. In a telephone-exchange system, a metallic-circuit line, one side or branch of which contains a polarized annunciator having contact-points by which the circuit is open while the annunciator indicates a call, and is normally grounded at the central office and the other side or branch of which is normally open at the central office, in combination with switch apparatus by which the line is disconnected from such ground connection while switched for conversation, a vibrating bell at IIO the subscribers station, normally in the circuit of the line, a switch with contacts and connections by which the bell'is switched or shunted from the line while the subscribers telephone is switched for use, a test receiving instrument grounded on one side and connected on its other side to a plug or device adapted to be brought into connection with said normally open end of the line, and a battery in the circuit thereby established, the annunciator and battery being so connected into the circuit that the battery does not operate the annunciator, substantially as set forth.

7. In atelephone-exchange system, a metallic-circuit line,one side or branch of which contains an annunciator having contact-points by which the circuit is open while the annunciator indicates a call and is normally grounded at the central oiiice but disconnected from the ground while switched for conversation and the other side or branch of which is normally open at the central office, in combination with a vibrating bell at the subscribers station, a switch with contacts and connections by which the bell is switched or shunted from the circuit while the subscribers telephone is switched for use,v and a test wire or circuit at the central office, containing a test receiving instrument and battery, grounded at one end and connected at its other end to a test plug or device adapted to be brought into connection with the normally open end of the line, said annunciator and battery being so constructed and connected that when thus connected in a circuit the battery does not operate the annunciator, substantially as set forth.

S. In a telephone-exchange system, a metallic-circuit line one side or branch of which contains an annunciator having contact-points by which the circuit is open While the annunciator indicates a call and is normally grounded at the central office and the other side or branch of which is normally open at the central office, in combination with switch apparatus by which the line is disconnected from such ground connection while switched for conversation, a vibrating bell at the subscribers station normally in the circuit of the line but switched or shunted from such circuit while the subscribers telephone is switched for conversation, a test receiving instrument at the central office grounded on one side and connected on its other side to a plug or device adapted to be brought into connection with the normally open end of the line, and a battery in the circuit thereby established, said annunciator and battery being so constructed and connected that when thus connected into a circuit the battery does not operate the annunciator, substantially as set forth.

D. In a telephone-exchange system, a metallic-circuit line normally disconnected from the ground at the subscribers station, one

side or branch of which is normally connected with the ground at the central office but disconnected from such ground connection while switched for conversation and has an annunciator normally in its circuit with contactpoints by which the circuit is open while the annunciator indicates a call and the other branch of which is normally open at the central office, in combination with a vibrating bell at the subscribers station, normally in the circuit of the line but switched or shunted from the circuit while the subscribers tele phone is switched for use, and a test Wire or circuit at the central office, containing a test receiving instrument and abattery, grounded on one side and connected on its other side to a plug or device adapted to be brought into connection with the normally open end of the line, substantially asset forth.

l0. In a telephone-exchange system, a metallic-circuit line norm ally disconnected from the ground at the subscribers station, one side or branch of which is normally connected with the ground at the central ofiice and has an annunciator normally in its circuit with contact-points by which the circuit is open while the annunciator indicates a call and the other side or branch of which is normally open at the central office, in combination with switching apparatus by which such ground connection at the central office is broken while the line is switched for conversation, a vibrating bell at the subscribers station normally in the circuit of the line, a switch with contacts and connections by which the bell is switched or shunted while the subscribers telephone is switched for use, a test receiving instrument at the central office grounded on one side and connected on its other side to a plug or device adapted to be brought into connection with the normally open end of the line, and a battery in the circuit thereby established, substantially as set forth.

11. In a telephone-exchange system, a metallic-circuit line normally disconnected from the ground at the subscribers office, one side or branch of which contains a polarized annunciator normally in its circuit with contact-points by which the circuit is open While the annunciator indicates a call and is normally grounded at the central office but disconnected from the ground While the line is switched for conversation and the other side or branch of Which is normally open at the central office, in combination with a callinggenerator at the subscribers station, contactpoints and connections by which the line is grounded while the generator is operated with the generator in circuit between such ground connection and the normal ground at the central office, a vibrating bell normally in the circuit of the line at the subscribers station but switched or shunted from circuit While the subscribers telephone is switched for use and a test wire or circuit containing a test receiving instrument and a battery,

IOO

IIO

grounded at one endv and connected at its other end toa plugv or devicel adapted tobe brought into-connection' with the normally open end of theli-ne', substantially as set forth.

l2. In a telephone-exchange system', a metallic-circuit line normally disconnected from the ground at the subscribers'station, one side or branch of Which contains a line-annunciator having contact-points by whichv the circuit is openfwhile the annunciator indi- Cates a call and is normally grounded at the, centraly ofce and the other side or branchfof which is normally open at the central ofce, inv combination withA switching apparatus to disconnect the line from its. normal connectionv with the ground While it is switched` for use', av calling-generator at the subscribers station, contact-points andl connections by which the line is' grounded While the generator is operated Withthe generator between such ground connection and the normal ground connection of the l-ine at the central office, a vibrating bell at the subseribers station' normally in the circuit of the line, a switch with contactsv and connections by which Ithe bell is switched or shunted from the circuit while the subscribers telephone is switched for-use, a test receiving instrument at the central ofce, grounded onA one side and connected on its other side toa plug or device adapted to be brought into connection with the normally open end of the line, and a battery in the circuit thereby established, substantially as set forth.

In Witness whereof I hereunto subscribe my name this 24th day of June, 1890.

c MILO G. KELLOGG.A

Witnesses:

W. MATTLE, C. STRICHOHAPELL- 

